1. Field of the Invention
The present invention relates to a method of using foam fractionation to remove proteins and other undesirable molecules from aqueous tobacco extract. More particularly, the present invention relates to a method of treating and modifying aqueous tobacco extract to enhance the extent and efficiency of the removal of proteins and other undesirable molecules from aqueous tobacco extract.
2. Description of the Related Art
Adsorptive bubble separation techniques, also known as foam fractionation, for separating and removing soluble compounds, are known in the art. The techniques have been applied to the separation of proteins, ions, metals, surfactants, and other particles such as activated carbons, clays, and plastics. For example, U.S. Pat. No. 5,653,867, issued to Jody, et al., teaches a method for separating acrylonitrile butadiene styrene (ABS) plastics from high impact polystyrene (HIPS). The extent and efficiency of separation are enhanced by selectively modifying the effective density of the HIPS using a solution having the appropriate density, surface tension, and pH, such as acetic acid and water or hydrochloric acid, salt, surfactant, and water. Further, U.S. Pat. No. 5,629,424, issued to Armstrong, et al., teaches an adsorptive bubble separation process, whereby a solution of optically active isomers and a chiral collector having a chiral center and a structure capable of interacting with an enantiomer or a diastereomer is formed, and a gas is bubbled through the solution to form bubbles having the chiral collector and the enantiomer or diastereomer adsorbed thereto. The bubbles are collected and allowed to collapse to form a liquid fraction separate from the solution, thereby producing an enriched concentration of the enantiomer or diastereomer. Also, U.S. Pat. No. 3,969,336, issued to Criswell, teaches a method of separating and concentrating soluble proteins from a whey protein solution via foam fractionation, and U.S. Pat. No. 5,951,875 and PCT WO 98/28082, both issued to Kanel, et al., teach a system for dewatering (i.e., concentrating) ruptured algal cells via adsorptive bubble separation techniques.
Thus, a process is needed to remove soluble proteins from aqueous tobacco extract via foam fractionation, combined with the treatment and/or modification of the tobacco extract to enhance the extent and efficiency of chemical removal, and further combined with the application of the resultant treated tobacco extract to tobacco sheet material.